The purpose of this longitudinal, multi-method study is to investigate the impact of prenatal exposure to cigarettes on the development of self-regulation over the first 2 years of life. Because most women who smoke cigarettes during pregnancy also have partners who smoke, children's exposure to environmental tobacco smoke (ETS) will also be examined. Cigarette exposure has been associated with a number of regulatory outcomes such as behavior problems, conduct disorder, and attention problems in later childhood. However, little is known about the developmental pathways to these self-regulatory outcomes among cigarette exposed children or about mediators and moderators of risk. Specific aims of this study are as follows: 1) examine direct effects of prenatal and ETS exposure on child regulation;2) examine the association between prenatal exposure and language development and the association between language development and self-regulation at 24 months;3) examine the role of parenting as the proximal mediator of the association between cigarette exposure and child outcomes such as reactivity and regulation at 9 and 16 months and self-regulation at 24 months;4) examine if a cumulative family risk score, including parenting, moderates the association between cigarette exposure and child outcomes. The final sample will consist of 150 women who smoke during pregnancy and 100 non-smoking women with no ETS exposure recruited prenatally, and followed for 2 years postnatally. Assessments of physiological and behavioral reactivity and regulation will be conducted at 2, 9, and 16 months of age. These include autonomic measures such as respiratory sinus arrythmia during sleep at 2 months, and during affect arousing procedures at 9 and 16 months, as well as observational assessments of reactivity and regulation of arousal. In addition, assessments of focused attention using both physiolgoical (e.g., Heart Rate) and observational measures will be conducted at 9 and 16 months. Finally, assessments of toddler self-regulation (effortful control, compliance, behavior problems, and internalization of rules) and language development will be conducted at 24 months of age. Parenting and risk variables will be assessed at each age as potential mediators or moderators of risk. The study is guided by a developmental psychopathology framework and transactional models of child development emphasizing multiple pathways to risk. It is anticipated that this study will enrich our understanding of pathways to self-regulatory problems among children of cigarette smoking mothers and reasons for heterogeneity in outcomes among cigarette exposed toddlers.